Continental shelf series#

The oldest island, Kure Atoll, is almost 30 million years old, and is in the northwest the youngest, the “Big Island” of Hawaiʻi, is still forming in the southeast. Eventually, after millions of years, the extinct volcanoes sink back below the ocean surface through a combination of erosion and subsidence of the dense ocean crust. Once the new volcano moves far enough past the hot spot, it becomes dormant, allowing yet another new volcano to form over the hot spot. As the Pacific Plate moves over the hot spot, an erupting shield volcano builds up from the ocean’s bottom and emerges as an island.

The island chain is shaped by the slow northwesterly motion of the Pacific tectonic plate over a mantle hot spot, moving a few inches each year. The relatively narrow shelf, which rapidly drops to depths of 3,000 to 4,000 meters, is a byproduct of the now inactive subduction zone that shaped much of the southwestern U.S.Īlthough part of the Pacific Region, Hawai'i stands alone geologically. To the south, in central and southern California, the San Andreas Fault forms the boundary between the south-moving North American Plate and the north-moving Pacific Plate.

Continental shelf series#

The processes affecting this geologically complex area have influenced the development of the Cascade Range, the Cascade volcanoes, and a series of ocean trenches and faults. In the northern portion of the region near Washington, Oregon, and northern California, the relatively small Juan de Fuca Plate is subducting under the North American tectonic plate. The Pacific OCS Region is shaped by an active geological margin. To the east of the Aleutian Island chain is the Gulf of Alaska (3,000 to 4,000 meters deep), an ecologically productive part of the northern Pacific Ocean. The Aleutian Island chain forms the southern border of the Bering Sea this 1000-mile-long volcanic island arc separates the deep Aleutian trench (with depths of 7,000 to nearly 8,000 meters) to the south from the shallower Bering Sea to the north. The eastern half of this sea is a relatively shallow (less than a 100 meters deep), while the western portion reaches depths of 3,000 to 4,000 meters. South of the Bering Strait is the ecologically productive Bering Sea. The Bering Strait is a narrow and shallow channel that has periodically formed a land bridge between Eurasia and the Americas during prehistoric glacial ages. Travelling counter-clockwise, one passes through the broad Chukchi Sea into the narrow and shallow Bering Strait. The Beaufort Sea has a narrow shelf, many submarine canyons, and is covered by ice during the dark winters. The north-eastern part of the region contains the Beaufort Sea, which is part of the Arctic Ocean. The Alaska OCS Region, which is the largest, has diverse geography, the longest coastlines, and the deepest water.